NAME

       Mail::DKIM::DNS - performs DNS queries for Mail::DKIM

VERSION

       version 1.20230212

DESCRIPTION

       This is the module that performs DNS queries for Mail::DKIM.

CONFIGURATION

       This module has a couple configuration settings that the caller may want to use to
       customize the behavior of this module.

   $Mail::DKIM::DNS::TIMEOUT
       This global variable specifies the maximum amount of time (in seconds) to wait for a
       single DNS query to complete. The default is 10.

   Mail::DKIM::DNS::resolver()
       Use this global subroutine to get or replace the instance of Net::DNS::Resolver that
       Mail::DKIM uses. If set to undef (the default), then a brand new default instance of
       Net::DNS::Resolver will be created the first time a DNS query is needed.

       You will call this subroutine if you want to specify non-default options to
       Net::DNS::Resolver, such as different timeouts, or to enable use of a persistent socket.
       For example:

         # first, construct a custom DNS resolver
         my $res = Net::DNS::Resolver->new(
                           udp_timeout => 3, tcp_timeout => 3, retry => 2,
                        );
         $res->udppacketsize(1240);
         $res->persistent_udp(1);

         # then, tell Mail::DKIM to use this resolver
         Mail::DKIM::DNS::resolver($res);

   Mail::DKIM::DNS::enable_EDNS0()
       This is a convenience subroutine that will construct an appropriate DNS resolver that uses
       EDNS0 (Extension mechanisms for DNS) to support large DNS replies, and configure
       Mail::DKIM to use it. (As such, it should NOT be used in conjunction with the resolver()
       subroutine described above.)

         Mail::DKIM::DNS::enable_EDNS0();

       Use of EDNS0 is recommended, since it reduces the need for falling back to TCP when
       dealing with large DNS packets. However, it is not enabled by default because some
       Internet firewalls which do deep inspection of packets are not able to process
       EDNS0-enabled packets. When there is a firewall on a path to a DNS resolver, the EDNS0
       feature should be specifically tested before enabling.

AUTHORS

       •   Jason Long <jason@long.name>

       •   Marc Bradshaw <marc@marcbradshaw.net>

       •   Bron Gondwana <brong@fastmailteam.com> (ARC)

THANKS

       Work on ensuring that this module passes the ARC test suite was generously sponsored by
       Valimail (https://www.valimail.com/)

COPYRIGHT AND LICENSE

       •   Copyright (C) 2013 by Messiah College

       •   Copyright (C) 2010 by Jason Long

       •   Copyright (C) 2017 by Standcore LLC

       •   Copyright (C) 2020 by FastMail Pty Ltd

       This library is free software; you can redistribute it and/or modify it under the same
       terms as Perl itself, either Perl version 5.8.6 or, at your option, any later version of
       Perl 5 you may have available.